OBJECTIVES: To develop and clinically evaluate an ultrasonic tissue characterization unit. METHODS EMPLOYED: We have completed the construction of an ultrasonic tissue analyser which provides far more qualitative and quantitative data on ultrasonic parameters than are currently available with any other imaging device. This analyser measures such variable factors as sound velocity, maximum and minimum reflections and the complex impedance of tissue interfaces. We are currently in the process of interfacing this unit with a new clinical scanner and will soon begin to acquire clinical scans for evaluation.